MetaEfficient

Office Building Is 100% Sewer-Free

by Justin Thomas • September 8, 2008

The sewer systems we use today are entirely ineffectual and unnecessary. The primary flaw in our design is that we use fresh water to dispose of feces. This is perhaps the most ineffectual thing to do with human manure — it pollutes fresh water, and it requires municipalities to maintain extremely costly sewage treatment infrastructures. Even after treatment, sewage can still wreck havoc on rivers and groundwater.

The most effective and straightforward thing to do with sewage is to compost it (or use it to produce fuel). It’s a valuable resource.

The toilets on each of the three floors connect via stainless steel chutes to five Clivus Multrum composting systems in the building’s basement. The toilets emit no odors, because all the waste is collected in the basement and fans ensure that no odor escapes the composting containers.

The system is maintained and emptied by the Clivus Multrum company through a service contract. Every day the university maintenance staff wipes down the toilets and adds a can of wood chips or bark mulch to each toilet. Every six months, the compost (which no longer resembles feces) is removed from the system and used as a fertilizer.

Because of this system, the C. K. Choi building uses just 500 liters of water per day (132 gallons), a similarly-sized conventional building uses an average of 7,000 liters of water a day (1850 gallons) or fourteen times as much water.

But about the water from sinks and other systems? This graywater is filtered and pumped into a 300-foot-long outdoor planter bed with lilies. The final discharge is used to irrigate plants. A test by the city of Vancouver of the fecal coliform counts of the discharged water showed that it contained less than 10 CFU per 100 milliliters (by comparison swimming is permitted in water with up to 200 CFU per 100 milliliters).

The building also captures rainwater: the rain is in a 7,000-gallon tank below a staircase. It is used to irrigate the landscape, which is bordered by thirsty ginkgo trees.

What this example clearly shows is that modern buildings can do quite well without a connection to a municipal sewage system. The maintaining the building’s composting system is probably less overall than a building with flushing toilets.

More information on this topic (including many other case studies) can be found in the excellent Composting Toilet System Book by David Del Porto and Carol Steinfeld.

I am building a house soon and would like one composting toilet. One of my friends has one in Australia and has no problems as long as the fan goes all the time. I live in a tropical country though and I am very concerned with insects infesting the compost. Does anyone have any info on composting toilets in tropical humid environments?

No, it’s not. The building and composting toilets are now 12 years old and I don’t see any mention of it smelling.

Odors are avoided eliminated multiple ways:

With the foam-flush toilets, the experience is just like a regular toilet only with almost no water. No odors.

With the open composting toilets, there is a negative pressure (air is sucked into the toilet) from a small, low-power fan. That keeps odors from coming into the room.

The addition of woodchips does two things. First, it covers the feces, so the smell is capped. Second, as noted by other commenters, the carbon in the woodchips mixes with the nitrogen in the urine and feces so that composting happens. Compost with a proper C-N ratio is a very low-odor process that’s entirely different from the septic conditions you’re used to smelling in an outhouse.

So between all these different parts of the system, you end up with no odors.

I visited the University of British Columbia about 7 years ago and saw this building when it was pretty new. Although solar panels are not evident on the roof, it has a bunch of other green components to the site and it was built in 1996 before we had PV of the quality and efficiency common today. Also of note is that Vancouver and the peninsula on which the campus are located are not exactly known for an excess of sunny days! This building was very state of the art green when built, and the fact that the composting toilets still work is to be noted!

That’s a truly neat system. It’s encouraging when a building is designed from the ground up to be highly eco-friendly. They could potentially collect the grey water and use it for flushing or adding moisture to the compost.

There’s no water in the toilets, just a chute that goes down into the basement. I think the wood chips fall into the composting containers and cover the feces, controlling odor and assisting in the composting process.